2206-P: Insulin Resistance May Enhance the Diagnostic Reproducibility of the 1-Hour Oral Glucose Tolerance Test

Introduction and Objective: After extensive epidemiologic review, the International Diabetes Federation (IDF) has stated that using the 1h-OGTT to diagnose diabetes (DM) is less expensive and time-consuming than the 2h-OGTT and leads to better detection of cardiometabolic risk than the 2h-OGTT. However, no data exists on the reproducibility of the diagnosis of DM by the 1h-OGTT. We aimed to (a) determine reproducibility of the diagnosis of DM by the 1h-OGTT, and (b) identify characteristics which favor reproducibility. Methods: Two 1h-OGTTs were performed 10±7 (mean±SD) days apart in 140 individuals (male: 61%, age: 40±11y, BMI: 27.8±4.5 kg/m2). IDF criteria for 1h-glucose were used to diagnose glucose tolerance status: normal glucose tolerance (NGT) 155 mg/dL, intermediate hyperglycemia (IH) 155 - 208 mg/dL, and DM ≥209 mg/dL. Insulin resistance (IR) was assessed with HOMA-IR. For the diagnosis of DM, reproducibility was evaluated with the kappa-statistic (Excellent: 0.81-1.0, Substantial: 0.61 - 0.80, Moderate: 0.41 - 0.60, Fair to Poor: 0.00 - 0.40). Results: DM was diagnosed in 24% (33/140) of enrollees. At OGTT-1, the prevalence of DM was 20% (28/140). At OGTT-2, the prevalence of DM was 19% (26/140). The kappa-statistic for the reproducibility of the diagnosis of DM was in the substantial category with a value of 0.73 (95% CI: 0.58-0.87). Overall, DM was detected in 21 persons at both OGTTs (non-switchers) and 12 persons were switchers with DM at one OGTT and NGT (5/12) or IH (7/12) at the other OGTT. Compared to switchers, non-switchers were more IR with higher HOMA-IR (4.24±2.53 vs. 2.42±1.52, P=0.03) and higher 1h glucose levels (253±53 vs. 219±6 mg/dL, P=0.03). Conclusion: As reproducibility for DM diagnosis by the 1h-OGTT is substantial, but not excellent, it is necessary to determine how to increase reproducibility so that individuals diagnosed with DM at the second OGTT but not the first, are not lost to follow-up. As IR was higher in individuals who had DM at both OGTTs, determining the link between IR and higher reproducibility of the 1h-OGTT may be key. Disclosure A. Shah: None. A. Bharadwaj: None. G. Smith: None. K. Ntabadde: None. C. DuBose: None. D.B. Sacks: Other - Crada; Current; Sebia. A. Sumner: None.